1. Field of the Disclosure
The disclosure relates to system-in packages, and more particularly, to system-in packages that include through vias formed in stacked chips and in stacked dummy substrates and utilize metal plugs formed in the through vias for electrical interconnection between the stacked chips.
2. Brief Description of the Related Art
Semiconductor wafers are processed to produce IC (integrated circuit) chips having ever-increasing device density and shrinking feature geometries. Multiple conductive and insulating layers are required to enable the interconnection and isolation of the large number of semiconductor devices in different layers. Such large scale integration results in an increasing number of electrical connections between various layers and semiconductor devices. It also leads to an increasing number of leads to the resultant IC chip. These leads are exposed through a passivation layer of the IC chip, terminating in I/O pads that allow connections to external contact structures in a chip package.
Wafer-Level Packaging (WLP) commonly refers to the technology of packaging an IC chip at wafer level, instead of the traditional process of assembling the package of each individual unit after wafer dicing. WLP allows for the integration of wafer fabrication, packaging, test, and burn-in at the wafer level, before being singulated by dicing for final assembly into a chip carrier package, e.g., a ball grid array (BGA) package. The advantages offered by WLP include less size (reduced footprint and thickness), lesser weight, relatively easier assembly process, lower overall production costs, and improvement in electrical performance. WLP therefore streamlines the manufacturing process undergone by a device from silicon start to customer shipment. While WLP is a high throughput and low cost approach to IC chip packaging, it however invites significant challenges in manufacturability and structural reliability.